FIG. 1 illustrates a mobile device 100, which is for example capable of communicating according to a number of different communication standards via one of a number of mobile network masts 102, 104, 106 and 108. For example, different regions may comprise communication infrastructures based on different communication standards. In the example of FIG. 1, the mast 102 in one region for example supports communications according to the GSM (global system for mobile communications) standard, the mast 104 in another region for example supports communications according to the UMTS (universal mobile telecommunications system) standard, the mast 106 in yet another region for example supports communications according to the WiMax (world interoperability for microwave access) standard, and the mast 108 for example supports communications according to the LTE (Long Term Evolution) standard. It is desirable that the mobile device 100 may communicate via any of the mobile network masts 102 to 108, and thus it is capable of communications according to all of the standards.
Each of the mobile communication standards is for example associated with a different transmission frequency. For example, communications according to the GSM standard may be transmitted at frequencies of 900 MHz or 1.8 GHz, communications according to the UMTS standard at 1.95 GHz, communications according to the WiMax standard at 2.7 or 3.5 GHz, and communications according to the LTE standard at 4.5 GHz. Thus, to be able to support more than one of the above communications standards, the transmission circuitry present in the mobile device 100 should be capable of transmission at any of the associated frequencies.
FIG. 2 illustrates an example of multi-standard transmission circuitry 200 of the mobile device 100. A data signal to be transmitted has been modulated to provide in-phase and quadrature components I and Q. These I and Q data signals are provided to a first transmission branch 201, and in particular to corresponding digital-to-analog converters (DACs) 202 and 204, the outputs of which are in turn coupled to corresponding low pass filters 206 and 208. The outputs from filters 206 and 208 are in turn coupled to corresponding mixers 210 and 212, which perform frequency up conversion of the filtered analog I and Q data signals, by multiplying them with corresponding frequency signals LO1I and LO1Q respectively. The outputs of mixers 210 and 212 are combined and provided to a power amplifier 214, which amplifies the signal to provide an RF signal for transmission via an antenna (not illustrated in FIG. 2) of mobile device 100.
Furthermore, the I and Q data signals are provided to a second transmission branch 220, which comprises the same components as the first transmission branch 201, but in which the mixers 210, 212 multiply the filtered digital data signals by frequency signals LO2I and LO2Q respectively, different to signals LO1I and LO1Q.
The transmission branch 201 supports one communications standard, while the transmission branch 220 supports another standard. Thus, the filters 206, 208, carrier frequencies, and power amplifiers 214 of each branch 201, 220 are for example selected based on the particular standard to be supported.
A drawback with the transmission circuitry 200 is that it is costly in terms of silicon area due to the two transmission branches, and the cost is even greater if extended to support more than two standards, by adding additional transmission branches.